8-oxoguanine riboswitches in bacteria detect and respond to oxidative DNA damage.

Riboswitches rely on structured aptamer domains to selectively sense their target ligands and regulate gene expression. However, some riboswitch aptamers in bacteria carry mutations in their otherwise strictly conserved binding pockets that change ligand specificities. The aptamer domain of a riboswitch class originally found to selectively sense guanine forms a three-stem junction that has since been observed to exploit numerous alterations in its ligand-binding pocket.

Variants of the guanine riboswitch class exhibit altered ligand specificities for xanthine, guanine, or 2'-deoxyguanosine.

The aptamer portions of previously reported riboswitch classes that sense guanine, adenine, or 2′-deoxyguanosine are formed by a highly similar three-stem junction with distinct nucleotide sequences in the regions joining the stems. The nucleotides in these joining regions form the major features of the selective ligand-binding pocket for each aptamer. Previously, we reported the existence of additional, rare variants of the predominant guanine-sensing riboswitch class that carry nucleotide differences in the ligand-binding pocket, suggesting that these RNAs have further diversified their structures and functions.

Translation initiation factors GleIF4E2 and GleIF4A can interact directly with the components of the pre-initiation complex to facilitate translation initiation in Giardia lamblia.

Translation initiation factor eIF4F is essential for cap-dependent translation initiation in eukaryotes. eIF4F is a trimeric complex consisting of a scaffold protein eIF4G, cap-binding protein eIF4E and DEAD-box RNA helicase eIF4A. eIF4F binds to the 5' cap structure of the mRNA through eIF4E and facilitates the binding of the preinitiation complex (PIC) via protein-protein interactions of eIF4G with eIF3 in mammals or with eIF5 in yeast.